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Help Please - No Voltage at Tstat but 26 volts at control board and transformers

Help Please - No Voltage at Tstat but 26 volts at control board and transformers


  #1  
Old 07-23-14, 05:52 PM
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Question Help Please - No Voltage at Tstat but 26 volts at control board and transformers

I purchased a foreclosed home (I live there now) with two identical furnaces and a/c units for each floor. The home, and I assume furnaces, are about 14 years old. They run on natural gas and are located in the basement. One is working great, the other is not functioning at all, and the Tstat isn't reading voltage/getting power (I connected an old Tstat (one that doesn't require batteries, and it didn't power up). At present, I am trying to turn the blower to 'on' and get that running.

Here is what I know:

1. This unit is in Wisconsin with wide ranging temperatures.

2. Furnace is a Thermo Pride CHB-50N.

3. I have power at the control board (White-Rodgers 50A50-13) so when I push the door safety button the light goes on for a second or two and then remains off indicating no issues with the board.

4. I have checked the voltage on the control board at R and C and the read is 26 volts.

5. I have checked the voltage on the out-side of the transformer that sits next to the control board inside the furnace and the out read is 26 volts.

6. I have checked the voltage on a second transformer (does this make sense?) that is attached outside the furnace on its side and the out read is 26 volts.

6. I have checked the voltage at the Tstat at R and C and it registers between 1 and 2 volts. Tstat doesn't seem to be getting what it needs.

7. My furnace does not have a fuse on any line-in power wires that I have been able to locate. I have checked and checked a few more times out of frustration in trying to resolve this problem. This was based on many forum reads.

8. My furnace does not have any drain check-valves that I have been able to find that would cause the system to stop. This was based on many forum reads. The system has not run, to my to knowledge, for at least a few months.

9. The furnaces have multiple add-ons: durozone multiline dampers/zone systems, a durozone comfort control system, Aprilaire humidifier, etc.

Any thoughts would be greatly appreciated. I have read many forum notes without success over the last few days and my head is spinning. Thank you in advance for your help!
 
  #2  
Old 07-23-14, 06:13 PM
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Welcome to the forums.

You've confirmed the voltage between R and C at the control board and it's 26vac. That means it's not going to be a transformer or fuse problem.

If you have the voltage at the board but not at the thermostat then it means the wiring is defective, spliced somewhere or cut. You'll have to trace the wire and look for problems.

In the pic of your board below...... try a jumper between R and G and see if the blower starts.

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If the blower works then it sounds like a Durozone issue which will require some equipment part numbers. Usually the thermostat connects to the durozone board and then that board connects to the White Rodgers board.
 
  #3  
Old 07-23-14, 06:20 PM
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Your thermostat is going to be connected to your Durozone control board.

Do you see any fuses on that board?
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Photo and image hosting, free photo galleries, photo editing

A picture of your zone control board would be great but the model number of it might be enough for us to offer more assistance.
 
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Old 07-23-14, 08:12 PM
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Thank you all thus far for the replies. I appreciate it greatly!

PJmax - Thank you for the welcome and advice. I am definitely interested in learning this trade. I will try to tie R and G together and see if the blower starts and let you know, but it may have to wait until the morning. I also am reading Houston204's suggestions and am wondering where I'd find the Durozone control board. Where is that usually located? Is it a inside the furnace or within the section of duct work where I see a small device and a section of the duct system inserted. I am certainly new at this so please bear with me. Thank you for your help!

Houston204 - Thank you for the advice. Where would you normally find the Durozone control board? I would like to look for a fusem but haven't seen anything like the diagram you posted. Attached to the duct work, I see a small device (transformer sized) that says Autotrol model 150, but that certainly isn't big enough to contain a control board the size you posted. Please bear with me. Thank you!!

P.S. I will take some pictures of anyone thinks that can help. Please advise. Thank you so much!
 
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Old 07-23-14, 08:21 PM
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That Autotrol device sounds like a duct damper operator.

Pictures would be great. http://www.doityourself.com/forum/el...-pictures.html
 
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Old 07-23-14, 09:32 PM
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Here are some pics - not sure I have what's needed, but please let me know.

The final two pictures are both in the rafters of the basement a few feet apart. I'm not sure if they are for each different floor...















 
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Old 07-24-14, 05:47 AM
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Zone control boards are usually near the furnace and have a dozen multi conductor wires connected to them.

The stats, dampers, furnace, a transformer and a duct sensor.
 
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Old 07-24-14, 09:55 AM
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Durozone Control System and Functioning Blower Using Bridge

I should have noticed the sixth picture was a DuroZone cover. Underneath is a Model SMZ-SW Zone Control System. I don't see any fuses. I am adding a picture below. Anything I can check on this?

I bridged R and G on the furnace control board and the blower started.

Any new thoughts based on these latest updates?

Thank you again so much for you help!

 
  #9  
Old 07-24-14, 10:08 AM
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Identify your thermostat wire on that board and measure for 24vac R to C.
Check incoming power at the furnace terimals then check the transformer terminals.

I will try to bring up a manual when I get home.
I just google the make and first 4 or 5 digits of the model.
 
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Old 07-24-14, 10:34 AM
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DuroZone System Updates

The R and C on the DuroZone Control system that leads to the furnace (top left on diagram) read 27 volts. I included a picture of the wiring diagram below. The R and W for Zone 1 read 27 volts. The R and W for Zone 2 read 2 volts.

Houston204: Thank you. A couple of follow-ups: when you refer to incoming power at the furnace terminals and the transformer terminals, is that different than what I did yesterday? I read 26vac out of the transformers (would I still need to confirm power in if I have power out?) Could you also verify what you mean by furance terminals? I previously confirmed the voltage between R and C at the control board at 26vac.

 
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Old 07-24-14, 10:43 AM
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DuroZone System Updates #2

I also read 26 vac across 1 & 2 of the panel equipment terminal strip and each panel zone terminal that is in use
 
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Old 07-24-14, 04:55 PM
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The damper transformer connected to 1 and 2 is what I was calling incoming power.


Looks like your zone control board requires a single stage heat pump with separate O and B terminals that runs on batteries.

Where is the stat C wire connected at your zone control board?

I only see 1 wire at furnace C and the 1 and 2 terminals.

If I were to guess I'd say the equipment terminals power the stats so stat C connects to the furnace C terminal along with the wire that is already there. You can disconnect furnace R then measure R to W at the stat to prove this.

What stat do you have connected to zone 1?
 
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Old 07-24-14, 05:12 PM
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Your zone 1 stat will control if you are in Heat or Cool mode.

Zone 2 is only able to provide heating or cooling if Zone 1 is in that mode (but not necessarily calling for operation).

The board that I posted gives zone 2 more control.
 
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Old 07-24-14, 06:01 PM
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Thank you for getting back to me, Houston204. I think I posted the wrong wiring diagram from the DuroZone system. Here is the other picture in the manual. Can you review and let me know what you think. Thank you!

 
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Old 07-24-14, 06:44 PM
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Where is your thermostat common connected at this time?
 

Last edited by Houston204; 07-24-14 at 07:26 PM.
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Old 07-24-14, 06:48 PM
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http://www.durodyne.com/durozone/SMZ-SWLR.pdf

The SMZ-SW is a simple zoning system incorporating individual thermostats and zone dampers to provide comfort and economy.
The Zone 1 Thermostat has a Sub-Base which acts as the master control to determine if heating or cooling is desired and if
the fan should be on constantly or just when the equipment calls.
Yep, your zone 1 stat must have separate O and B terminals.

Post a picture of the connections at the stat.
What is the make and model of your stat?
 
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Old 07-24-14, 06:54 PM
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Stat common should connect to the furnace C.
 
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Old 07-24-14, 07:01 PM
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That is a funny color code that your installer is using.

I would have wired the stat...
R = red
B = blue
O = orange
W = white
Y = yellow
G = green
C = brown (and connect stat C to the Equip C)

But...

At this point it would be easier for you just to connect the yellow wire to C at the stat and connect the other end to Equip C along with the brown wire that is there now and keep the odd color code.
 
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Old 07-24-14, 07:31 PM
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The stats are both Robertshaw 9600.

First floor stat, which is working, is wired:


Second floor stat, which is not working, is wired (second floor stat has blue wire instead of yellow at the Y):


Can you confirm your advice regarding the yellow wire? Connect on the panel board to C and also on the DuroZone board to C under the Equip terminal strip?

Thank you!! I really appreciate your help.
 
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Old 07-24-14, 08:06 PM
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No, I cannot confirm anything now.
It should not be able to work as you have shown.

The thermostat Y terminal controls the cooling compressor.
You have a yellow wire connected to Y at your zone 1 stat.
The yellow wire is not connected to anything at the zone control board.
How is it able to cool?

It is like finding out that Chuckie doesn't have his batteries after he has been speaking in that old movie.

Do you have a control board between the stat and the displayed zone control?

Do you have a third thermostat in your house that controls a second outdoor unit?

The zone control requires a separate O and B terminal and you have neither terminal on that stat.
http://www.robertshawtstats.com/imag.../150-1401H.pdf
 
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Old 07-24-14, 08:46 PM
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I am very sorry Houston204. You are correct. I think Chuckie has batteries after all but I am no expert. There is a third stat in the basement that was blocked by items from the move. I am adding its picture below. Same make/model thermostat. Here's what I know now. This all started when I wanted the a/c turned on for my top floor (it was 90 degrees here a couple of days ago). The top floor stat did not respond and I found the second a/c unit not working. I now have that a/c unit working by turning the basement unit to cool AND moving the 'set temperature' setting below the actual temperature in the basement. I confirmed just setting the basement stat on cool and having the top floor stat on cool with a ''set temp' below the actual temp did NOT turn the blower or a/c unit on. That seems silly and I am wondering if something is wired incorrectly? At this point, I don't understand the zones in my house (I will read up on this) or how to get the top unit working without the basement unit receiving warm or cold air at the same time. It does appear, however, that all systems are able to function by using the basement unit. But it would certainly be nice to only use the top floor stat. It seems that it doesn't have an effect on anything. Sorry to have come around in such a wide manner. I am glad I found someone who knows their ****, ah, I mean stuff

Any last suggestions or comments on the system would be awesome. Thank you again for seeing me through this.

 
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Old 07-25-14, 06:18 AM
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Your zone 1 stat is a different model than the zone 2 since it has an O and a B terminal as required.

The batteries should be changed annually.

That zone control only supports 2 thermostats.
You can flip the power switch to the furnace off to prove which 2 stats connect to that furnace.

I'd say that the stat with yellow at Y is not going to the zone control.
 

Last edited by Houston204; 07-25-14 at 07:32 AM.
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Old 07-25-14, 08:01 AM
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Thank you, Houston204. The basement (zone 1) stat is a 9610 (looked the same from the outside and should have paid more attention). The other two stats in the house are 9600.

So, top floor (blue at Y) stat 9600 is zone 2 of the zone control. And you are correct, the main floor stat 9600 (yellow at Y) is not going to the zone control.

Can you recommend a link to read regarding how the two two-zone stats communicate? I still cannot get the zone two stat to function on its own. It only seems that the zone 1 stat is working. I have air flow in zone 2 when the zone 1 stat is turned on and the zone 2 stat is off. I am not sure if that's normal.

I feel much better about the status of the system at this point in general though, so thank you again for your help. All the best!
 
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Old 07-25-14, 03:50 PM
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Houston204:

I guess with all of the developments I forgot the original post and question: I do not have 24 vac at the zone 2 thermostat. Shouldn't there be power there, and if so, how do I fix it based on my setup? Thank you!
 
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Old 07-25-14, 05:10 PM
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Your thermostats do not have C.
What are you measuring R to?

When you give zone 2 a cooling demand do you get 24 volts between zone 2 Y and furnace C at the board?
 
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Old 07-25-14, 06:47 PM
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I was measuring R to W, R to Y and R to G. They all read about 2 vac. If I measured one of the three and closed the loop by asking the stat to engage that process, the read would drop to 0 as expected. The thermostat on its own zone reads 26 vac for all R to W, R to Y, R to G, so I expected the same on the zone 2 stat.

I will need to measure zone 2 Y and furnace C once I get the multimeter back. Unfortunately I had to give that back to its owner. Have a great weekend!
 
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Old 07-25-14, 08:11 PM
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You can also verify that the dampers get the signal to open when a demand is present.



SMZ-SW SYSTEM CHECK-OUT PROCEDURE
The following check-out procedure requires a voltmeter set to read 24 volts A.C.. If, after the check-out procedure is completed,
the SMZ-SW panel and dampers are operating correctly, but the system is not functioning properly, check your wiring carefully.
The most common problems experienced are a misplaced wire, a bad connection or a broken wire. If none of these seems to be
the problem, check your thermostats and equipment. YOU MUST PERFORM THE FOLLOWING TEST PROCEDURES
IN THE ORDER SHOWN. DO NOT SKIP ANY OF THESE STEPS. Place all damper switches in “O”
open position .
1. You must have 24 volts across R & C of the SMZ-SW Panel Equipment Terminal Strip. (This powers the SMZ-SW panel
and your equipment).
2. You must have 24 volts across 1 & 2 of the SMZ-SW Panel Equipment Terminal Strip and every 1 & 2 of each SMZ-SW
Panel Zone terminal. (This powers the dampers).
3. To test the operation of the SMZ-SW panel, you must disconnect all thermostats. With the thermostats disconnected and
24 volts as described in #2 above, all dampers should be open. (If the dampers are not open, go to step 4).
3A. To test the heat mode, connect R & B at the SMZ-SW Panel Zone 1 Terminal Strip. (This sets the panel to heat). Zone 1 will
be activated when you jump R & W at the SMZ-SW Zone 1 Panel Terminal Strip. (All zone dampers, except Zone 1 will close
and the furnace will turn on). Zone 2 or Zone 3 can be activated by jumping W & R at the corresponding SMZ-SW Zone 2 or
Zone 3 Terminal Strips. If the furnace does not activate, with R & B connected and R & W, (or W & R of Zone 2 or Zone 3)
jumped, test for 24 volts across C & W at the SMZ-SW Panel Equipment Terminal Strip. If voltage reading is 24 volts, panel is
okay.
3B. To test the cool mode, disconnect the R & B connection made for the heat mode check. Connect R & O at the SMZ-SW
Panel Zone 1 Terminal Strip. (This sets the panel to cool and the indicator light on the equipment relay will come on).
Zone 1 will be activated when you jump R & Y at the SMZ-SW Panel Zone 1 Terminal Strip. (All zone dampers except
zone 1 will close, and the air conditioning will come on). Zones 2 or 3 can be activated by jumping R & Y at the SMZ-SW
Zone 2 or Zone 3 Terminal Strips. If the air conditioning does not activate with R & O connected and R & Y, (or R & Y
of Zone 2 or Zone 3) jumped, test for 24 volts across C & Y at the SMZ-SW Panel Equipment Terminal Strip. If voltage
reading is 24 volts, panel is okay.
3C. To test the Fan, jump R & G at the SMZ-SW Panel Zone 1 Terminal Strip. Be sure at least one Damper Switch is in “open”
“(O)” position. The fan should activate. If the fan does not activate, with R & G jumped, test for 24 volts across C & G
at the SMZ-SW Panel Equipment Terminal Strip. If voltage reading is 24, panel is okay.
4. To test the damper operation, perform step #3A, checking for 24 volts across 1 & 4 of every SMZ-SW Panel Zone Terminal
Strip when that zone is activated, and for “0” volts at 1 & 4 of every SMZ-SW Panel Zone Terminal Strip that is not
activated. (IMPORTANT: This test will work only if at least one zone is activated. If no zone is activated, all terminal 1 &
4 readings will be 24 volts). If all readings are correct, the panel is operating correctly. If a damper is not functioning but
the SMZ-SW Panel has checked out okay, check for 24 volts across terminals 1 & 2 on the damper motor. If you have 24
volts, disconnect the terminal 4 connection to the damper. Jumping terminals 4 & 5 and the damper should open. (It will
take 30 to 60 seconds for a damper to fully open). When you disconnect the jumper from terminals 4 & 5 the damper
should close. If the damper tested does not operate as described, the problem could either be binding damper linkage,
the blade movement is being obstructed, or you could have either an incorrect or a defective motor. (With multiblade
dampers, it is possible to connect the motor to the linkage 180º “out of phase”, which causes the damper to be open
when it should be closed and closed when it should be open). If this is the case, remove the motor and rotate the linkage
180º and then re-install the motor (this applies to Power Open/Close Dampers only-not the Spring Return Dampers).
 
 

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